[unreadable] Our long-term goal is to gain insight into the pathogenesis of invasive anal cancer (IAC) in men who have sex with men (MSM), in order to identify molecular targets for detection and treatment of anal neoplasia. Although anal cancer is rare in the general population, even before the HIV epidemic, MSM were known to be at greatly increased risk for invasive anal cancer. Over the past 30 years the incidence of anal cancer among MSM, especially those infected with HIV, has further increased. While identification and treatment of lesions at highest risk for progression to invasive anal cancer would prevent progression to invasive anal, the lack of sensitive and specific tests for identifying AIN-3/ACIS has impeded the establishment of routine screening and treatment of MSM: cytology is insensitive and non-specific, and screening on the basis of detection of high risk HPV types, central to development of IAC, has low specificity since most MSM are infected with high risk HPV. We propose to examine the DNA methylation status of 20 genes in anal biopsies from HIV positive and negative men with and without various degrees of anal neoplasia and cancer. Silencing of genes by aberrant DNA methylation of CpG islands in the promoter region is now recognized as playing a major role in the pathogenesis of cancer, and is believed to occur early in carcinogenesis. Using quantitative MethyLight and previously collected anal biopsy material from men.with and without AIN-3/ACIS or IAC, we propose to assess the methylation profile of 20 genes of interest, and construct a panel of hypermethylated genes with maximal sensitivity and specificity for IAC/ACIS. We will assess the correlation between detection of gene hypermethylation in anal biopsy tissues and swabs. Finally, we will compare the relative sensitivity and specificity of identification of AIN-3/ACIS by cytology, detection of high risk types of HPV DNA and detection of the panel of hypermethylated genes using anal swabs samples previously collected from a population of MSM who underwent anal cytology and HPV screening and biopsy. [unreadable] [unreadable]